As is well known, a vehicle is comprised of one or more differential gears and each of them is used for transmitting torque provided to a differential case to a pair of output shafts while allowing differential motion therebetween.
Some differential gears have means for limiting or locking differential motion under proper control, thereby preventing wheels from losing traction even when any of the wheels loses contact with the ground. They are often referred to as “lock-up differentials.” In the other differential gears in contrast, these differential gear sets are rotatable freely from these differential cases and the differential gears are comprised of means for controllably transmitting torque from the differential cases to the differential gear sets. The latter are often referred to as “free-running differentials” and are used for realizing so-called “part-time 4WD” configuration or such purposes.
Any of the aforementioned respective means can be realized by a combination of a clutch combined with a differential gear and an actuator for connecting and disconnecting the clutch for example.
While a solenoid can exert a force in either direction, there may be a case where the solenoid is so structured as to exert a force generally in a single direction and a return spring is used in combination therewith for the purpose of simplifying its action. The following documents disclose related subject matter.
Japanese Patent Application Laid-open No. 2011-099460
Japanese Patent Application Laid-open No. 2011-122653